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Alert Notice 353: Monitoring of Blazars requested for VERITAS/XMM TOO

Campaign was updated in Special Notice #62 and Special Notice #77.

July 11, 2007: Our assistance has been requested by Dr. Markus Boettcher, Ohio University, in a study he and colleagues are making of several blazars. The targets are being intermittently monitored by VERITAS (the Very Energetic Radiation Imaging Telescope Array System), a four-telescope collection designed to detect astrophysical sources of very high energy (VHE) gamma-rays that is located at the Fred Lawrence Whipple Observatory in Arizona. If a VHE gamma-ray outburst is detected by VERITAS, target-of-opportunity observations with the Newton X-ray Multi-Mirror (XMM) telescope will be triggered. Since VERITAS is not regularly monitoring the targets, optical monitoring is crucial to alert the VERITAS collaboration to a high state of any one of the blazars on the list in order to initiate VERITAS observations.

The XMM observing season has begun, so AAVSO observers are requested to monitor the target blazars from now through at least May 2008, when the current XMM observing cycle ends. Dr. Boettcher and colleagues have submitted a Chandra proposal along the same lines that, if funded, would extend the study throughout most of 2008.

The target list is given below. Finder charts for nine of the ten targets are available through VSP (http://www.aavso.org/vsp), but two of these do not have sequences. Also, the sequences for three targets are not completely available in VSP right now but are available through pre-existing AAVSO charts, so please follow the URLs given for these stars. The tenth target does not have either a finder chart or a sequence available right now.

Dr. Boettcher has requested the following hierarchy of observations: Cousins R nightly or multiple times per night; add B if possible; one UBVRI set per night if possible; signal-to-noise ratio of 50 or better.

VERITAS uses R-band threshold magnitudes to trigger observations. The table below contains the threshold R magnitude for each target as well as an approximate V-magnitude trigger value. If you observe a target at or brighter than the threshold, please notify AAVSO Headquarters immediately by submitting your observation via WebObs. If the target is below the threshold, please try to submit your observation within 24 hours. The astronomers need to be alerted within one to two days, and we have to allow time for confirmation, so please do not delay in reducing your data and submitting your observations.